A1C of 6.5% is an average glucose of 140 mg/dL

Estimated average glucose at A1C 6.5%

140 mg/dL

In mmol/L: 7.8 mmol/L
A1C entered: 6.5%
ADA range: the range the ADA uses to diagnose diabetes

6.5% translates to an average glucose of about 140 mg/dL, which is 7.8 mmol/L in the units used across the UK, Australia and Canada. The IFCC equivalent of the A1C itself is close to 48 mmol/mol.

The ADA uses this range diagnostically. One practical note: for values this high the conversion is extrapolating well beyond where most of the study data sat, so treat the estimated average as an order of magnitude rather than a precise figure.

A1C 6.5% is the exact threshold the ADA uses in diagnosing diabetes, which makes it the second most-searched value here. The ADA normally requires two abnormal results, or one plus clear symptoms, before a diagnosis — so a first 6.5% is a reason to see a clinician rather than a conclusion in itself.

The scale is gentler than it looks. Moving from here to 6.6% shifts the estimated average by only about 3 mg/dL, to roughly 143 mg/dL — well inside the 0.5-point band the assay is allowed to wander within.

How readily an individual glycates varies, which is one reason a continuous-monitor average and a laboratory A1C often disagree in the same person even when both are measured properly.

Time spent in range and time spent high or low are separate questions from the average, and they matter clinically in ways an average cannot capture.

The window is rolling rather than fixed, so an A1C taken today and one taken a month from now overlap substantially in the period they describe.

Repeat testing exists because of this. The ADA asks for confirmation before diagnosing precisely because one measurement of anything, including this one, carries error worth ruling out.

Convert a different A1C value

A1C to estimated average glucose, 6.0% to 7.0%
A1C	eAG (mg/dL)	eAG (mmol/L)
6.0%	126 mg/dL	7 mmol/L
6.1%	128 mg/dL	7.1 mmol/L
6.2%	131 mg/dL	7.3 mmol/L
6.3%	134 mg/dL	7.4 mmol/L
6.4%	137 mg/dL	7.6 mmol/L
6.5%	140 mg/dL	7.8 mmol/L
6.6%	143 mg/dL	7.9 mmol/L
6.7%	146 mg/dL	8.1 mmol/L
6.8%	148 mg/dL	8.2 mmol/L
6.9%	151 mg/dL	8.4 mmol/L
7.0%	154 mg/dL	8.5 mmol/L

Computed with eAG (mg/dL) = 28.7 x A1C - 46.7 (Nathan 2008). mmol/L is derived from mg/dL using the glucose factor 18.0182.

Estimated average glucose (ADAG / Nathan) — eAG (mg/dL) = 28.7 x A1C - 46.7. Verified 2026-07-30 against Nathan et al., Diabetes Care 2008 (ADAG study) (A population regression: in the ADAG study, individuals at the same A1C had meaningfully different mean glucose. The A1C assay itself carries about +/- 0.5 percentage points under NGSP certification.)

Official sources

Nathan DM et al., Translating the A1C Assay Into Estimated Average Glucose Values, Diabetes Care 2008 — The ADAG study that produced the eAG equation used on this page.
American Diabetes Association — Standards of Care in Diabetes — Where the A1C ranges quoted here are defined.
NGSP — A1C assay standardisation and certification criteria — Why two lab results half a point apart can mean nothing changed.

Frequently asked questions

An A1C of 6.5% equals what blood sugar?

140 mg/dL is the estimate, which is 7.8 mmol/L. It follows directly from the ADAG regression applied to 6.5%, and represents a population average rather than your personal figure.

How is 6.5% classified?

The ADA describes 6.5% as the range the ADA uses to diagnose diabetes. That is a definition of a numeric range rather than a diagnosis: the ADA asks clinicians to confirm results with a repeat test and to read them alongside your history.

Would a different lab report the same 6.5%?

Not necessarily. Analytical methods vary between laboratories, and a point-of-care fingerstick can read differently from a venous draw, so comparisons are cleanest within one lab.

Is 6.5% a target?

This page converts a number rather than recommending one. Glycemic targets are individualised by a clinician according to your diagnosis, your other results and your risk of hypoglycaemia.

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